Conventional tweeters utilize standard ferrous magnets in conjunction with a voice coil to control the speaker cone, dome, or other diaphragm. However, such magnets are relatively large and heavy. Further, such magnets produce significant stray magnetic fields which require bulky shielding to contain, thereby further increasing both the size and weight of the speaker.
However, it is desirable in high fidelity speakers to place the tweeter as close to the woofer as possible so that the sound appears to come from a single source. To achieve this, a sub-compact tweeter assembly is required. It has been found that such a sub-compact design can be achieved by utilizing high energy magnets, such as magnets formed of neodymium-iron-boron (sometimes hereinafter referred to as "neodymium magnet") in place of the standard ferrous magnets. Since such magnets provide a force or energy which, weight for weight, is roughly twenty times stronger than that of conventional magnets, the speakers may operate with a magnet which is roughly the size of a quarter. Further, these smaller magnets generate less stray magnetic field and this field can be contained in a relatively small ferrous yoke assembly. The result is a sub-compact high performance tweeter which provides minimum stray field problems.
However, in order for the speaker to track transients such as those evident in drum hits or acoustic guitar music, the tweeter must be able to handle high levels of power, yet remain cool in operation so as to avoid damage to the speaker coils or the diaphragm. But, one disadvantage of using the compact magnets is that they provide significantly less thermal mass for heat dissipation than more conventional designs and this has been found to present a significant limitation on the levels of power available from such speakers, and thus on the performance thereof. It would therefore be desirable if the advantages of the sub-compact, high-energy magnet tweeters could be achieved while improving the heat management in such tweeters so as to permit high levels of power to be handled.